For words that have only three letters, there isn't any 4th letter. One example is with the word “increase”, there are no a lot more letters afterwards and therefore should be the word "include". The word “addict” is from the BIP39 wordlist however you would've utilized “addi” for “addict”. This https://todaybookmarks.com/story18936583/the-ultimate-guide-to-bip39-seed-phrase-github